Archives for August, 2009

This guy is Allo Diavolo: He was a circus daredevil. At the dawn of the 20th century he worked on a number of stunts dressed in his ominous horned outfit. These days a lot of people, including me, have heard of him as an example in the pages of physics textbooks. In my case it…

I think we’ve developed a nice theme over the last few weeks, gradually working our way through a less well-behaved function – the triangle wave – and trying to find various series expansions for it. “Well-behaved” is kind of a term of art, which mathematicians use as shorthand for long strings of caveats about differentiability…

We’ve seen that it’s pretty easy to determine your latitude using the sun as a reference point. All you need is a shadow and chart that was easily available to sailors of previous centuries and you’re set. Finding your longitude is another story. The reason for the difference in difficulty is one of time. The…

Holy moly, if you want to see a great post you should read Ethan’s post on the solar analemma. If you photograph the sun in the sky at the same time each day, it won’t be in the same spot. The orbital motion of the earth, your location on the curve of the earth, and…

Not much meat here at the Built on Facts table today. Our research group is embarking on a new project with the Office of Naval Research, and today was the official all-day meeting with the officer in charge of coordinating the various projects in his part of the ONR funding structure. We’ve spent a lot…

Sorry for the two-day delay. The personal business to which I alluded kept me out until yesterday morning, delaying this post until today. I hope it’s decent for all that! This week, the same function as last week. There’s nothing so special about the function itself, but it does serve as a nice Rorschach blot…

In the last post I made an offhand mention of wave dispersion, which is the phenomena of different wavelengths propagating a different speed. In general this does exactly what it sounds like it should. It disperses the light. If you start off with a tightly grouped bunch of runners, the pack will spread out as…

All right, the answer to yesterday’s question about the maximum speed of a stadium wave, as many commenters rightly said, is “as fast as you want.” The comments went into some depth on this, and I like the way Zifnab put it: I mean, if you’ve got two independent agents doing their thing, the “speed”…

The wave. We’ve talked about it before. It’s where people in a stadium stand up and sit down in sequence so that a wave of standing people travels around the circumference of the stands. They have a typical speed of around 12 m/s, though it is by no means entirely universal. You could certainly imagine…

Let’s say there’s an interesting but somewhat obscure book I’m interested in. Say, Electromagnetic Pulse Propagation in Causal Dielectrics. It’s a very technical work about a very specific subject, so the total print run was probably very small. Maybe a few hundred or a thousand or so? I have no idea, but it can’t be…